/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.feilong.lib.springframework.util;

/**
 * Assertion utility class that assists in validating arguments.
 *
 * <p>
 * Useful for identifying programmer errors early and clearly at runtime.
 *
 * <p>
 * For example, if the contract of a public method states it does not
 * allow {@code null} arguments, {@code Assert} can be used to validate that
 * contract. Doing this clearly indicates a contract violation when it
 * occurs and protects the class's invariants.
 *
 * <p>
 * Typically used to validate method arguments rather than configuration
 * properties, to check for cases that are usually programmer errors rather
 * than configuration errors. In contrast to configuration initialization
 * code, there is usually no point in falling back to defaults in such methods.
 *
 * <p>
 * This class is similar to JUnit's assertion library. If an argument value is
 * deemed invalid, an {@link IllegalArgumentException} is thrown (typically).
 * For example:
 *
 * <pre class="code">
 * Assert.notNull(clazz, "The class must not be null");
 * Assert.isTrue(i > 0, "The value must be greater than zero");
 * </pre>
 *
 * <p>
 * Mainly for internal use within the framework; consider
 * <a href="https://commons.apache.org/proper/commons-lang/">Apache's Commons Lang</a>
 * for a more comprehensive suite of {@code String} utilities.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @author Colin Sampaleanu
 * @author Rob Harrop
 * @since 1.1.2
 */
public abstract class Assert{

    /**
     * Assert a boolean expression, throwing an {@code IllegalStateException}
     * if the expression evaluates to {@code false}.
     * <p>
     * Call {@link #isTrue} if you wish to throw an {@code IllegalArgumentException}
     * on an assertion failure.
     * 
     * <pre class="code">
     * Assert.state(id == null, "The id property must not already be initialized");
     * </pre>
     * 
     * @param expression
     *            a boolean expression
     * @param message
     *            the exception message to use if the assertion fails
     * @throws IllegalStateException
     *             if {@code expression} is {@code false}
     */
    public static void state(boolean expression,String message){
        if (!expression){
            throw new IllegalStateException(message);
        }
    }

    /**
     * Assert a boolean expression, throwing an {@code IllegalArgumentException}
     * if the expression evaluates to {@code false}.
     * 
     * <pre class="code">
     * Assert.isTrue(i &gt; 0, "The value must be greater than zero");
     * </pre>
     * 
     * @param expression
     *            a boolean expression
     * @param message
     *            the exception message to use if the assertion fails
     * @throws IllegalArgumentException
     *             if {@code expression} is {@code false}
     */
    public static void isTrue(boolean expression,String message){
        if (!expression){
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an object is not {@code null}.
     * 
     * <pre class="code">
     * Assert.notNull(clazz, "The class must not be null");
     * </pre>
     * 
     * @param object
     *            the object to check
     * @param message
     *            the exception message to use if the assertion fails
     * @throws IllegalArgumentException
     *             if the object is {@code null}
     */
    public static void notNull(Object object,String message){
        if (object == null){
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that the given String is not empty; that is,
     * it must not be {@code null} and not the empty String.
     * 
     * <pre class="code">
     * Assert.hasLength(name, "Name must not be empty");
     * </pre>
     * 
     * @param text
     *            the String to check
     * @param message
     *            the exception message to use if the assertion fails
     * @see StringUtils#hasLength
     * @throws IllegalArgumentException
     *             if the text is empty
     */
    public static void hasLength(String text,String message){
        if (!StringUtils.hasLength(text)){
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an array contains elements; that is, it must not be
     * {@code null} and must contain at least one element.
     * 
     * <pre class="code">
     * Assert.notEmpty(array, "The array must contain elements");
     * </pre>
     * 
     * @param array
     *            the array to check
     * @param message
     *            the exception message to use if the assertion fails
     * @throws IllegalArgumentException
     *             if the object array is {@code null} or contains no elements
     */
    public static void notEmpty(Object[] array,String message){
        if (ObjectUtils.isEmpty(array)){
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that the provided object is an instance of the provided class.
     * 
     * <pre class="code">
     * Assert.instanceOf(Foo.class, foo, "Foo expected");
     * </pre>
     * 
     * @param type
     *            the type to check against
     * @param obj
     *            the object to check
     * @param message
     *            a message which will be prepended to provide further context.
     *            If it is empty or ends in ":" or ";" or "," or ".", a full exception message
     *            will be appended. If it ends in a space, the name of the offending object's
     *            type will be appended. In any other case, a ":" with a space and the name
     *            of the offending object's type will be appended.
     * @throws IllegalArgumentException
     *             if the object is not an instance of type
     */
    public static void isInstanceOf(Class<?> type,Object obj,String message){
        notNull(type, "Type to check against must not be null");
        if (!type.isInstance(obj)){
            instanceCheckFailed(type, obj, message);
        }
    }

    /**
     * Assert that {@code superType.isAssignableFrom(subType)} is {@code true}.
     * 
     * <pre class="code">
     * Assert.isAssignable(Number.class, myClass, "Number expected");
     * </pre>
     * 
     * @param superType
     *            the super type to check against
     * @param subType
     *            the sub type to check
     * @param message
     *            a message which will be prepended to provide further context.
     *            If it is empty or ends in ":" or ";" or "," or ".", a full exception message
     *            will be appended. If it ends in a space, the name of the offending sub type
     *            will be appended. In any other case, a ":" with a space and the name of the
     *            offending sub type will be appended.
     * @throws IllegalArgumentException
     *             if the classes are not assignable
     */
    public static void isAssignable(Class<?> superType,Class<?> subType,String message){
        notNull(superType, "Super type to check against must not be null");
        if (subType == null || !superType.isAssignableFrom(subType)){
            assignableCheckFailed(superType, subType, message);
        }
    }

    /**
     * Assert that {@code superType.isAssignableFrom(subType)} is {@code true}.
     * 
     * <pre class="code">
     * Assert.isAssignable(Number.class, myClass);
     * </pre>
     * 
     * @param superType
     *            the super type to check
     * @param subType
     *            the sub type to check
     * @throws IllegalArgumentException
     *             if the classes are not assignable
     */
    public static void isAssignable(Class<?> superType,Class<?> subType){
        isAssignable(superType, subType, "");
    }

    private static void instanceCheckFailed(Class<?> type,Object obj,String msg){
        String className = (obj != null ? obj.getClass().getName() : "null");
        String result = "";
        boolean defaultMessage = true;
        if (StringUtils.hasLength(msg)){
            if (endsWithSeparator(msg)){
                result = msg + " ";
            }else{
                result = messageWithTypeName(msg, className);
                defaultMessage = false;
            }
        }
        if (defaultMessage){
            result = result + ("Object of class [" + className + "] must be an instance of " + type);
        }
        throw new IllegalArgumentException(result);
    }

    private static void assignableCheckFailed(Class<?> superType,Class<?> subType,String msg){
        String result = "";
        boolean defaultMessage = true;
        if (StringUtils.hasLength(msg)){
            if (endsWithSeparator(msg)){
                result = msg + " ";
            }else{
                result = messageWithTypeName(msg, subType);
                defaultMessage = false;
            }
        }
        if (defaultMessage){
            result = result + (subType + " is not assignable to " + superType);
        }
        throw new IllegalArgumentException(result);
    }

    private static boolean endsWithSeparator(String msg){
        return (msg.endsWith(":") || msg.endsWith(";") || msg.endsWith(",") || msg.endsWith("."));
    }

    private static String messageWithTypeName(String msg,Object typeName){
        return msg + (msg.endsWith(" ") ? "" : ": ") + typeName;
    }

}
